Gull-wing Door - Design Challenges

Design Challenges

Gull-wing doors have a somewhat questionable reputation because of early examples like the Mercedes and the Bricklin. The 300 SL needed the door design as its tubular frame race car chassis design had a very high door sill, which in combination with a low roof would make a standard door opening very low and small. The Mercedes engineers solved the problem by also opening a part of the roof. The Bricklin was a more conventionally-sized door but the actuation system was problematic in day-to-day use and led to unreliable operation until an aftermarket air-door upgrade was installed in all Bricklins. In addition, there was some concern that in making the doors as light as possible they wouldn't provide adequate protection in side-impact accidents. There was, however, no indication that this concern was justified.

The DeLorean solved these problems by using a solid-steel torsion bar (supplied by Grumman Aircraft Engineering Corporation) to counterbalance a full-sized door and then used simple pneumatic struts similar to those found in hatchback cars to open the doors and damp their movement.

Other disadvantages of the system were not so easy to address. For example, the gull-wing design makes creating a convertible version of the car harder, as the hinges would be removed with the roof, and standard doors would be needed for the convertible. Mercedes did so when replacing the gullwing coupe altogether with the 300SL roadster in 1958. It was never a concern for DeLorean since no convertible version was ever planned.

It also makes sealing the car against water leaks more difficult because of the shape and movement path of the door itself. Many DeLorean owners report leakage when taking their vehicles through automated car-washes because of the high-pressure water jets, though in ordinary rainfall the seals are more than adequate.